The present invention relates generally to a shoe having an ability to track the cumulative destructive compressions imparted to a shoe by its user and the ability to indicate that information to the user. More specifically, the present invention relates to an attachment of the shoe that measures the destructive compressions of the shoe, accumulates those compressions and displays the accumulation to the user.
Athletes must replace their shoes as the midsole foam wears due to the cumulative destructive compressions that occur from use. Delaying the replacement of the shoe will lead to injuries caused by the lower extremities absorbing more of the impact. In addition, changes in the characteristics of the midsole foam, such as shape and compression resistance, affects the users ability to control their biomechanical motion during their stance to foot swing phase, also known as the gait of the user, causing inefficiency and injury. Because the construction of the midsole includes microporous foam, detection of this cumulative destruction cannot be determined by a simple external examination. As with other microscopic failure modes, examining a device in a static condition does not predict the loss of performance in a kinetic condition, such as during a runner's heel strike through the roll off the toe. Typically, shoe manufacturers recommend discarding shoes every 400 miles. However, this varies depending on the number of compressions the shoe experiences during the recommended life. More specifically, the shoe manufacturers usually design their shoes to reach their end of life after approximately 400,000 compressions, which equates to 600 compressions per mile.
Shoe wear indicators are known in the art. For example, one reference discloses a wear indicator built into the shoe with a means to detect progressive loss of flexibility and cushioning of the shoe based upon the number of times it has been actuated and indicates this information to the user. In particular, the reference discloses a means to detect the actuation that is between the midsole and outersole of the shoe and uses a bladder. Changes in the bladder pressure are used to determine the shoes actuation.
Another example discloses a wear indicator for a shoe including an outsole and a midsole with wear indicators made of less compactible material vertically disposed within the midsole and a method to indicate the need to replace the shoe.
Another example discloses a shoe wear-out sensor that includes a detector for sensing a physical metric that wears out with the shoe, a processor, and an alarm for informing the user when the sole of the shoe is worn out. The detector is required to be a force sensing resistor or accelerometer and a processor configured to compare the acceleration against similar data of a new shoe. Additionally disclosed is a system including a detector, a processor which increments when the shoe is in use, and an alarm such as an LED or an audible device that is observable to the user during use.
Another example discloses a footwear having electronic circuitry associated with measuring usage comprising a power source, a first and second pressure switch which alternate between “on” and “off” and connected to a logic circuit with a decoder which sends information to a display mounted on the footwear.
Another example discloses a shoe wear indicator comprising an air bladder sensor unit, a microchip, a power supply/user interface and an interface cable housed within the insole. Further disclosed is a method of using the device in a combination of inserting the device into a shoe, using the shoe for physical activity, removing the device from the shoe, and downloading the usage data to the terminal.
Another example discloses a garment with a connected force sensor and a means of processing and analysing that sensor signal profile and then transmitting it to the wearer.
A disadvantage of the prior art is the placement of the device within the construction of the shoe, which requires that the design and manufacturing process of the shoe be altered. Furthermore, this requirement leads to the reduction in performance of the shoe both by the elimination of a portion of the cushioning foam and reduction in flexibility due to the addition of the device. For example, the placement of the device within the midsole or outsole requires the reengineering of the shoe to compensate for the loss of functionality, which would disallow the device from being incorporated in any existing shoe designs. Another example would be the incorporation of a less compactible material within the shoe which changes the supportive characteristics of the shoe design.
Another disadvantage of the prior art is the requirement of the sensor to be a combination of an air bladder and pressure sensor or a combination of an accelerator and force sensing resistor. The accuracy of these elements is affected by the environment around the sensor during use. For example, variations in atmospheric pressure or temperature may change the reference values needed to compare when the shoe is in use or not in use. In another example, the sensor is said to measure a physical metric that changes as the shoe wears out which requires that the sensor change correspondingly with the shoe. These disadvantages require a robust and complex analysis of the starting and ending state of the sensor throughout the shoe use and, in some cases, foreknowledge of the wear rate of the shoe.
Another disadvantage of the prior art is the inability to distinguish a non-destructive compression from a destructive compression. Although the art describes methods to make this comparison, such as the physical displacement of the sensor or the amount of acceleration above the minimal level, this analysis becomes more complicated as the shoe wears which will change the reference point, requiring a robust and complex analysis of the starting and ending state of the sensor. Other methods require foreknowledge of the user's weight, stance-to-foot swing phase and other values specific to the shoe construction.
Another disadvantage of the prior art is the requirement that the output of the information of the invention be transmitted outside the shoe or by removing the invention from the shoe and connected it to a terminal. In another art, the information is actively communicated to the user through a light or transmission while the device is in use. These elements may seem advantageous for some applications but the complexity of removing, analyzing the wear of the shoe, and reinserting the device back into the shoe greatly complicates both the use of the shoe and the interpretation of the use. This requirement increases user complexity and introduces the probability of errors and forgetfulness. For example, a blue wear indicator strip on the razor blade improved the user compliance better than other disassociated mnemonics. Furthermore, the communication of the device's information to the user during the device's use greatly complicates the designs, requiring that the indication means egress from the shoe or that the shoe be modified to allow egress in an unobtrusive way.
Yet another disadvantage of the prior art is the requirement that the device is constructed out of reusable materials which increases the cost of the device by the use of durable components that can be used again. Although this may be advantageous for some applications, the maintenance and reliability of such a reused device is an added burden to the user. For example, although the razor blade may be resharpened after it has reached its initial end of life, the complexity of sharpening it and the understanding of how many more sharpenings it should receive is more cumbersome than users are willing to tolerate and therefore they simply discard the used razor.
Accordingly, there is a need for a low cost device that measures the destructive compressions of the shoe in such a manner that it is self referencing and accumulates those compressions and can display the accumulation to the user within the shoe in a manner that is simpler for the user to interface with.